1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>Mu - linux/bootstrap/035compute_segment_address.cc</title>
<meta name="Generator" content="Vim/8.1">
<meta name="plugin-version" content="vim8.1_v1">
<meta name="syntax" content="cpp">
<meta name="settings" content="number_lines,use_css,pre_wrap,no_foldcolumn,expand_tabs,line_ids,prevent_copy=">
<meta name="colorscheme" content="minimal-light">
<style type="text/css">
<!--
pre { white-space: pre-wrap; font-family: monospace; color: #000000; background-color: #ffffd7; }
body { font-size:12pt; font-family: monospace; color: #000000; background-color: #ffffd7; }
a { color:inherit; }
* { font-size:12pt; font-size: 1em; }
.LineNr { }
.Constant { color: #008787; }
.Comment { color: #005faf; }
.Normal { color: #000000; background-color: #ffffd7; padding-bottom: 1px; }
.Identifier { color: #af5f00; }
.Delimiter { color: #c000c0; }
.cSpecial { color: #008000; }
-->
</style>
<script type='text/javascript'>
<!--
/* function to open any folds containing a jumped-to line before jumping to it */
function JumpToLine()
{
var lineNum;
lineNum = window.location.hash;
lineNum = lineNum.substr(1); /* strip off '#' */
if (lineNum.indexOf('L') == -1) {
lineNum = 'L'+lineNum;
}
var lineElem = document.getElementById(lineNum);
/* Always jump to new location even if the line was hidden inside a fold, or
* we corrected the raw number to a line ID.
*/
if (lineElem) {
lineElem.scrollIntoView(true);
}
return true;
}
if ('onhashchange' in window) {
window.onhashchange = JumpToLine;
}
-->
</script>
</head>
<body onload='JumpToLine();'>
<a href='https://github.com/akkartik/mu/blob/main/linux/bootstrap/035compute_segment_address.cc'>https://github.com/akkartik/mu/blob/main/linux/bootstrap/035compute_segment_address.cc</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr"> 1 </span><span class="Comment">//: ELF binaries have finicky rules about the precise alignment each segment</span>
<span id="L2" class="LineNr"> 2 </span><span class="Comment">//: should start at. They depend on the amount of code in a program.</span>
<span id="L3" class="LineNr"> 3 </span><span class="Comment">//: We shouldn't expect people to adjust segment addresses everytime they make</span>
<span id="L4" class="LineNr"> 4 </span><span class="Comment">//: a change to their programs.</span>
<span id="L5" class="LineNr"> 5 </span><span class="Comment">//: Let's start taking the given segment addresses as guidelines, and adjust</span>
<span id="L6" class="LineNr"> 6 </span><span class="Comment">//: them as necessary.</span>
<span id="L7" class="LineNr"> 7 </span><span class="Comment">//: This gives up a measure of control in placing code and data.</span>
<span id="L8" class="LineNr"> 8 </span>
<span id="L9" class="LineNr"> 9 </span><span class="Normal">void</span> <a href='035compute_segment_address.cc.html#L9'>test_segment_name</a><span class="Delimiter">()</span> <span class="Delimiter">{</span>
<span id="L10" class="LineNr">10 </span> <a href='011run.cc.html#L82'>run</a><span class="Delimiter">(</span>
<span id="L11" class="LineNr">11 </span> <span class="Constant">"== code 0x09000000</span><span class="cSpecial">\n</span><span class="Constant">"</span>
<span id="L12" class="LineNr">12 </span> <span class="Constant">"05/add-to-EAX 0x0d0c0b0a/imm32</span><span class="cSpecial">\n</span><span class="Constant">"</span>
<span id="L13" class="LineNr">13 </span> <span class="Comment">// code starts at 0x09000000 + p_offset, which is 0x54 for a single-segment binary</span>
<span id="L14" class="LineNr">14 </span> <span class="Delimiter">);</span>
<span id="L15" class="LineNr">15 </span> <a href='003trace.cc.html#L290'>CHECK_TRACE_CONTENTS</a><span class="Delimiter">(</span>
<span id="L16" class="LineNr">16 </span> <span class="Constant">"load: 0x09000054 -> 05</span><span class="cSpecial">\n</span><span class="Constant">"</span>
<span id="L17" class="LineNr">17 </span> <span class="Constant">"load: 0x09000055 -> 0a</span><span class="cSpecial">\n</span><span class="Constant">"</span>
<span id="L18" class="LineNr">18 </span> <span class="Constant">"load: 0x09000056 -> 0b</span><span class="cSpecial">\n</span><span class="Constant">"</span>
<span id="L19" class="LineNr">19 </span> <span class="Constant">"load: 0x09000057 -> 0c</span><span class="cSpecial">\n</span><span class="Constant">"</span>
<span id="L20" class="LineNr">20 </span> <span class="Constant">"load: 0x09000058 -> 0d</span><span class="cSpecial">\n</span><span class="Constant">"</span>
<span id="L21" class="LineNr">21 </span> <span class="Constant">"run: add imm32 0x0d0c0b0a to <a href='010vm.cc.html#L10'>EAX</a></span><span class="cSpecial">\n</span><span class="Constant">"</span>
<span id="L22" class="LineNr">22 </span> <span class="Constant">"run: storing 0x0d0c0b0a</span><span class="cSpecial">\n</span><span class="Constant">"</span>
<span id="L23" class="LineNr">23 </span> <span class="Delimiter">);</span>
<span id="L24" class="LineNr">24 </span><span class="Delimiter">}</span>
<span id="L25" class="LineNr">25 </span>
<span id="L26" class="LineNr">26 </span><span class="Comment">//: compute segment address</span>
<span id="L27" class="LineNr">27 </span>
<span id="L28" class="LineNr">28 </span><span class="Delimiter">:(before "End Transforms")</span>
<span id="L29" class="LineNr">29 </span><a href='031transforms.cc.html#L4'>Transform</a><span class="Delimiter">.</span>push_back<span class="Delimiter">(</span><a href='035compute_segment_address.cc.html#L32'>compute_segment_starts</a><span class="Delimiter">);</span>
<span id="L30" class="LineNr">30 </span>
<span id="L31" class="LineNr">31 </span><span class="Delimiter">:(code)</span>
<span id="L32" class="LineNr">32 </span><span class="Normal">void</span> <a href='035compute_segment_address.cc.html#L32'>compute_segment_starts</a><span class="Delimiter">(</span>program& p<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L33" class="LineNr">33 </span> <a href='003trace.cc.html#L96'>trace</a><span class="Delimiter">(</span><span class="Constant">3</span><span class="Delimiter">,</span> <span class="Constant">"transform"</span><span class="Delimiter">)</span> << <span class="Constant">"-- compute segment addresses"</span> << end<span class="Delimiter">();</span>
<span id="L34" class="LineNr">34 </span> <span class="Normal">uint32_t</span> p_offset = <span class="Comment">/*</span><span class="Comment">size of ehdr</span><span class="Comment">*/</span><span class="Constant">0x34</span> + <a href='001help.cc.html#L168'>SIZE</a><span class="Delimiter">(</span>p<span class="Delimiter">.</span><a href='011run.cc.html#L106'>segments</a><span class="Delimiter">)</span>*<span class="Constant">0x20</span><span class="Comment">/*</span><span class="Comment">size of each phdr</span><span class="Comment">*/</span><span class="Delimiter">;</span>
<span id="L35" class="LineNr">35 </span> <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">size_t</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i < p<span class="Delimiter">.</span><a href='011run.cc.html#L106'>segments</a><span class="Delimiter">.</span>size<span class="Delimiter">();</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L36" class="LineNr">36 </span> segment& curr = p<span class="Delimiter">.</span><a href='011run.cc.html#L106'>segments</a><span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">);</span>
<span id="L37" class="LineNr">37 </span> <span class="Normal">if</span> <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>start >= <span class="Constant">0x08000000</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L38" class="LineNr">38 </span> <span class="Comment">// valid address for user space, so assume we're creating a real ELF binary, not just running a test</span>
<span id="L39" class="LineNr">39 </span> curr<span class="Delimiter">.</span>start &= <span class="Constant">0xfffff000</span><span class="Delimiter">;</span> <span class="Comment">// same number of zeros as the p_align used when emitting the ELF binary</span>
<span id="L40" class="LineNr">40 </span> curr<span class="Delimiter">.</span>start |= <span class="Delimiter">(</span>p_offset & <span class="Constant">0xfff</span><span class="Delimiter">);</span>
<span id="L41" class="LineNr">41 </span> <a href='003trace.cc.html#L96'>trace</a><span class="Delimiter">(</span><span class="Constant">99</span><span class="Delimiter">,</span> <span class="Constant">"transform"</span><span class="Delimiter">)</span> << <span class="Constant">"segment "</span> << i << <span class="Constant">" begins at address 0x"</span> << <a href='010vm.cc.html#L408'>HEXWORD</a> << curr<span class="Delimiter">.</span>start << end<span class="Delimiter">();</span>
<span id="L42" class="LineNr">42 </span> <span class="Delimiter">}</span>
<span id="L43" class="LineNr">43 </span> p_offset += size_of<span class="Delimiter">(</span>curr<span class="Delimiter">);</span>
<span id="L44" class="LineNr">44 </span> assert<span class="Delimiter">(</span>p_offset < <a href='010vm.cc.html#L98'>SEGMENT_ALIGNMENT</a><span class="Delimiter">);</span> <span class="Comment">// for now we get less and less available space in each successive segment</span>
<span id="L45" class="LineNr">45 </span> <span class="Delimiter">}</span>
<span id="L46" class="LineNr">46 </span><span class="Delimiter">}</span>
<span id="L47" class="LineNr">47 </span>
<span id="L48" class="LineNr">48 </span><span class="Normal">uint32_t</span> size_of<span class="Delimiter">(</span><span class="Normal">const</span> segment& s<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L49" class="LineNr">49 </span> <span class="Normal">uint32_t</span> sum = <span class="Constant">0</span><span class="Delimiter">;</span>
<span id="L50" class="LineNr">50 </span> <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i < <a href='001help.cc.html#L168'>SIZE</a><span class="Delimiter">(</span>s<span class="Delimiter">.</span><a href='011run.cc.html#L113'>lines</a><span class="Delimiter">);</span> ++i<span class="Delimiter">)</span>
<span id="L51" class="LineNr">51 </span> sum += <a href='035compute_segment_address.cc.html#L56'>num_bytes</a><span class="Delimiter">(</span>s<span class="Delimiter">.</span><a href='011run.cc.html#L113'>lines</a><span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
<span id="L52" class="LineNr">52 </span> <span class="Identifier">return</span> sum<span class="Delimiter">;</span>
<span id="L53" class="LineNr">53 </span><span class="Delimiter">}</span>
<span id="L54" class="LineNr">54 </span>
<span id="L55" class="LineNr">55 </span><span class="Comment">// Assumes all bitfields are packed.</span>
<span id="L56" class="LineNr">56 </span><span class="Normal">uint32_t</span> <a href='035compute_segment_address.cc.html#L56'>num_bytes</a><span class="Delimiter">(</span><span class="Normal">const</span> line& inst<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L57" class="LineNr">57 </span> <span class="Normal">uint32_t</span> sum = <span class="Constant">0</span><span class="Delimiter">;</span>
<span id="L58" class="LineNr">58 </span> <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i < <a href='001help.cc.html#L168'>SIZE</a><span class="Delimiter">(</span>inst<span class="Delimiter">.</span><a href='011run.cc.html#L122'>words</a><span class="Delimiter">);</span> ++i<span class="Delimiter">)</span>
<span id="L59" class="LineNr">59 </span> sum += size_of<span class="Delimiter">(</span>inst<span class="Delimiter">.</span><a href='011run.cc.html#L122'>words</a><span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
<span id="L60" class="LineNr">60 </span> <span class="Identifier">return</span> sum<span class="Delimiter">;</span>
<span id="L61" class="LineNr">61 </span><span class="Delimiter">}</span>
<span id="L62" class="LineNr">62 </span>
<span id="L63" class="LineNr">63 </span><span class="Normal">int</span> size_of<span class="Delimiter">(</span><span class="Normal">const</span> word& w<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L64" class="LineNr">64 </span> <span class="Normal">if</span> <span class="Delimiter">(</span>has_argument_metadata<span class="Delimiter">(</span>w<span class="Delimiter">,</span> <span class="Constant">"disp32"</span><span class="Delimiter">)</span> || has_argument_metadata<span class="Delimiter">(</span>w<span class="Delimiter">,</span> <span class="Constant">"imm32"</span><span class="Delimiter">))</span>
<span id="L65" class="LineNr">65 </span> <span class="Identifier">return</span> <span class="Constant">4</span><span class="Delimiter">;</span>
<span id="L66" class="LineNr">66 </span> <span class="Normal">else</span> <span class="Normal">if</span> <span class="Delimiter">(</span>has_argument_metadata<span class="Delimiter">(</span>w<span class="Delimiter">,</span> <span class="Constant">"disp16"</span><span class="Delimiter">))</span>
<span id="L67" class="LineNr">67 </span> <span class="Identifier">return</span> <span class="Constant">2</span><span class="Delimiter">;</span>
<span id="L68" class="LineNr">68 </span> <span class="Comment">// End size_of(word w) Special-cases</span>
<span id="L69" class="LineNr">69 </span> <span class="Normal">else</span>
<span id="L70" class="LineNr">70 </span> <span class="Identifier">return</span> <span class="Constant">1</span><span class="Delimiter">;</span>
<span id="L71" class="LineNr">71 </span><span class="Delimiter">}</span>
<span id="L72" class="LineNr">72 </span>
<span id="L73" class="LineNr">73 </span><span class="Comment">//: Dependencies:</span>
<span id="L74" class="LineNr">74 </span><span class="Comment">//: - We'd like to compute segment addresses before setting up global variables,</span>
<span id="L75" class="LineNr">75 </span><span class="Comment">//: because computing addresses for global variables requires knowing where</span>
<span id="L76" class="LineNr">76 </span><span class="Comment">//: the data segment starts.</span>
<span id="L77" class="LineNr">77 </span><span class="Comment">//: - We'd like to finish expanding labels before computing segment addresses,</span>
<span id="L78" class="LineNr">78 </span><span class="Comment">//: because it would make computing the sizes of segments more self-contained</span>
<span id="L79" class="LineNr">79 </span><span class="Comment">//: (num_bytes).</span>
<span id="L80" class="LineNr">80 </span><span class="Comment">//:</span>
<span id="L81" class="LineNr">81 </span><span class="Comment">//: Decision: compute segment addresses before expanding labels, by being</span>
<span id="L82" class="LineNr">82 </span><span class="Comment">//: aware in this layer of certain argument types that will eventually occupy</span>
<span id="L83" class="LineNr">83 </span><span class="Comment">//: multiple bytes.</span>
<span id="L84" class="LineNr">84 </span><span class="Comment">//:</span>
<span id="L85" class="LineNr">85 </span><span class="Comment">//: The layer to expand labels later hooks into num_bytes() to teach this</span>
<span id="L86" class="LineNr">86 </span><span class="Comment">//: layer that labels occupy zero space in the binary.</span>
</pre>
</body>
</html>
<!-- vim: set foldmethod=manual : -->
|